Temperature control unit



April 28, 1953 A. J. HUCK 2 ,636,959

' TEMPERATURE CONTROL UNIT Filed April 10, 1950 2 SI'IEETS-SHEET l 12-14z' gz.

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April 28, 1953 v A. J. HUCK 2,636,959

TEMPERATURE CONTROL UNIT Filed April 10, 1950 2 SHEETS-SHEET 2 I 5 l 7y'hk 'e N Patented Apr. 28, 1953 TEMPERATURE CONTROL UNIT Alfred J. Huck,St. Louis, Mo., assignor to Knapp- Monarch Company, St. Louis, Mo., acorporation of Delaware Application April 10, 1950, Serial No. 155,073

3 Claims.

This invention relates to a temperature control unit of the generalcharacter shown in my copending applications, Serial No. 772,678, filedSeptember 8, 1947, and Serial No. 36,959, filed July 3, 1948, both nowabandoned, the present application being a continuation-impart of saidtwo copending applications. The temperature control unit hereindisclosed is of the "anticipating type, that is, a thermostat is mountedin a control housing remote from an electric blan et, heating pad or thelike, the temperature of which is to be controlled in accordance withthe control unit.

One object of the invention is to provide a remote control unit of thisgeneral character which cycles at a relatively high temperature due toan electrically operated thermostat heater incorporated in theconstruction of the thermostat and having no thermal relation to theblanket or other electrical appliance controlled thereby, the thermostatbeing adjustable to different temperature settings and maintaining theblanket at a substantially constant temperature somewhat lower than thetemperature of the thermostat itself.

Another object is to provide a thermostat which anticipates rise andfall in temperature of the blanket by providing a heat bridge acrosswhich heat is permitted to flow in such manner that the thermostat lagsbehind the temperature of its thermostat heater, the lag being increasedby including a mass that is first heated by the thermostat heater beforethe temperature thereof is transmitted through the heat bridge to thebimetal element in the thermostat.

Still another object is to provide a heat bridge which delays the heatfrom the thermostat heater to the bimetal during an approaching on cycleand stores heat from the bimetal heater for slow deliverance to thebimetal to thereby delay cooling of the bimetal during an approachingoff cycle.

A further object is to provide a temperature control unit wherein athermal cycling switch acts a percentage on type of control switch forcontrolling the current that flows through the heating element of ablanket or the like.

Still a further object is to provide a circuit arrangement wherein acycling type of control switch includes inherent in its design a meansto compensate for ambient temperature so that a warming blanket or thelike controlled by the switch unit will be maintained at a comfortabletemperature regardless of rise or fall in the room temperature.

An additional obiect is to provide a temperature control unit includinga cycling switch and means to compensate for room temperature, theswitch and the means each having a bimetal element which elements areseparate from each other so that the cycling switch element may operateat a higher and more reliable temperature and control the cycling withinrelatively close limits not possible if operated at room temperature,the room temperature responsive element then modifying the action of thecycling switch in accordance with room temperature so that thetemperature of the blanket is maintained at different desirable valuesregardless of rise or fall in room temperature surrounding the blanketand the control unit.

With these and other objects in View, my invention consists in theconstruction, arrangement and combination of the various parts of mytemperature control unit, whereby the objects contemplated are attained,as hereinafter more fully set forth, pointed out in my claims, andillustrated in the accompanying drawings, wherein:

Figure 1 is a perspective View of a temperature control unit embodyingmy present invention.

Figure 2 is an enlarged horizontal sectional view thereof as taken onthe line 2-2 of Figure 1.

Figure 3 is a vertical sectional view taken on the line 33 of Figure 2.

Figure 4 is a vertical sectional view taken on the line 44 of Figure 3.

Figure 5 is an enlarged sectional view on the line 5-5 of Figure 2; and

Figure 6 is an electro-diagrammatic view of the circuit used inconnection with the temperature control unit disclosed.

Figures 7 and 8 are enlarged vertical sectional views of the controlunit shown in Figure 3.

On the accompanying drawings I have used the reference numeral It toindicate a service plug from which wires l2 and I4 extend. Referring tothe diagram in Figure 6, the wire l2 extends directly to the heatingelement HE of an electric blanket or the like and the wire I 4 extendsto an on-off switch having control contacts [6 and. 18.

The contact i 8 is connected by a wire 20 to a compensator bimetal 28carrying a contact 26. The contact 28 is adapted to cooperate with acontact 24 on a timer bimetal 22 which is connected to an end 30 of atiming bimetal heater 32. From the heater 32, a wire 34 extends to asecondary control SC and a wire 36 extends therefrom to the heatingelement HE for completing the circuit.

A condenser 33 shunts the contacts 24 and 26 and the heater 32. Anindicator light such as a neon bulb ill is connected across the wires l2and 29 with a resistor t2 in series to out down the voltage to the bulbit.

The secondary control SC includes a voltage coil it, a fixed resistor itand a variable resistor 48 across the line from the wire 2 to the wire35. A series or current coil 55; is connected between the wires 3 andfit and is in series with secondary control contacts 52 and 54. Thecontacts t2 and 5d are normally engaged and. are. adapted to beseparated by the attraction of an armature 56 carrying the contact 52 acore 58 on which the coils 4 i and so are wound.

The elements it to 58 constitute a secondary control in the event ofdamage or other m alfunctioning of the temperature control unit and isoperable to ole-energize the warming. blanket or device controlled bythe unit and maintain it in the de-energized condition. The secondarycontrol, in other words, is asafety control and forms no part of mypresent invention, it being the subject matter of a copendingapplication, Serial No. 44,607, filed August. 17, 1948, now Patent No.2,592,525, dated April 15, 1952, and being claimed. therein.

Having described the electrical elements of my temperature control unit,I will now refer to the physical construction shown in Figures 1 to 5;The various elements. of the control. unit thus far described aremounted on a base plate til and covered by a housing 6-2 whicharrangement permits room temperature to act suiii'ciently by thermalconduction through the base plate and the housing to actuate thecompensator bimeta-l 28-.

The contact !8 (see Figure 8) is mounted on a switchblade 89 which iscontrolled by a cam 56-. The switch blade It is mounted on an ear 78aextending from a supporting bracket '58 and. insulated therefrom. Thecam- 66 is mounted on a shaft 58 having a: slot ill in which a blade 72extending from a control knob is is engaged. The blade when rotated itslimit ina counterclockwise direction is in the on position shown in.Figure '7 and engages a stoplugv l6 formed on the supporting bracket "idwhich is secured to the base 6d. The position shown in Figure 3 is withthe switch l 6-! 8' turned on and the control unitadjusted for low heat.The knob it can berotated about 189- degrees clcckwiseior' adjusting thecontrol unit for a progressively higher. heat and in the high. heatposition (Figirre 8) an extension 19 of the blade. '32 engages the. stoplug it:

The high-heat adjustment just referred. to is accomplished by the cam 55progressively raising a spring blade Bil which. is: connected with abracket 82 pivoted on a bolt: ils'andi providedwith a spring 80: tendingto rotate" the spring blade 83] in a clockwise direction. in Figure 3and against the cam 66. The compensator bimetal 28' is carried by thebracket 82 and accordingly its. contact. 26 is progressively moved intotighter engagement with. the contact as on the timer bimetal 22 as theknob 75 and the cam 66 are adjusted forahigher heat.

The. cam. 55 has a. notch 3'5 cooperating with a hump 21 on the switchblade 9 at the off end of the adjustment range; a projection 68 next tothe notch 6? serving to depress the hump. as the cam. is rota-tedcounter clocinwise' from the Figure. 3: position and thereby adjust the.switch ltl8 to the off position when the: hump 2 snaps into notch 6? asin Figure. Th h ater 32 for the bimetal 22 is wound around a layer ofmica 35 on a heat bridge element 33. This element may consist of arelatively thick bar of brass or the like in thermal contact with thebimetal element 22 as shown in Figure 5, the two being assembled inrelation to a bracket 33 mounted on an insulating plate 45 which in turnis mounted on the bracket 13. The means of mounting consists of a screw3-? through the bracket, the bimetal element and the heat bridge elementas shown in Figure 5, a nut 39 bein used to retain the bolt in positionand to clamp the end 33 of the heater 32 to the bimetal element.

Mounted on the blade '52 (see Figure 4) for rotation: therewith is atranslucent dial 4! provided with: suitable indicia as shown in Figure 1through which the. light of the indicator bulb 8 shines so that theposition of adjustment of the control unit can be readily determined atnight. A cover plate 41 on the housing 82 is provided with an.arc-shaped opening d9 through which the dial ll may be observed as theknob it is rotated.

Practical operation.

In the operation of the temperature control unit disclosed, the partsare. in the normal position when. cold as shown in Figure 3. The controlis in the ofi. position in Figure 7 so that current cannot flow from thelinev wire. 14 across the contacts 81 and. ['8 Arrows across the bimetalelements 22' and 2.3 in Figure 6 indicate the direction that theseelements warp when heated.

When the control knob 14 is rotated clockwise from. the position ofFigure 3., first the contacts 16. and it are. engaged for establishing acircuit from M" through Hi; l8, [9,, 2.9,. 28', 26-, 2t, 22,. 30., 32,3d, 50., 5.2,. 5 K and 36. to the heating element HE, the. current.returning through the wire [2 to. the source. of supply. The heatingelement heats up and so does, the heater 32. The heat in 32' passes. byconduction. through. the heat bridge element 33 to the. bimetal element22 to cause itsccntact 24 to move in a. direction tov lessen thepressure against the contact 26. The response of the. bimetal. element.22. to the heat of the heater 32-, however, is. laggarddue to theelement 33 constituting. a. heat bridge and being preferably ofconsiderable mass so as to. require a period of heatabsorption beforeit. can warp the element 22 suihciently to open the contacts 2 and 26.

When the warping. force. in 22 is sumcient, it will separate the.contact 24 from the contact 28 and this. will be accomplished withslight snap action inasmuch as. the contact 26 is a relatively small.magnet setin a cup 2.6a. as. best shown in Figure (land the contact 24isof ferrous material, the two. beingv silver-plated. to provideefficient contact surfaces- When the. contacts do open, arcing. is.reduced. by reason of. the condenser 38 shunting the. contacts and theheater- When the contact 24 disengages the contact 2.6.. the circuitthrough the heating element HE and the heater 32 isbroken. so that thebimetal element 22- andthe heat bridge 3% mas; start to cool down.

Since the; element. 3.3: has. considerable: mass: its cooling action;will be:- siow. so that it will. take some time for. the. contact: 24.-to re-engage the contactv 26-. The thermal. lag: introduced between theheater 32. and the. bimetal element 22 the heat bridge element 33! thus.produces a-relatively slow cycling of the control unit with the resultthat the unit continues. to repeat the cycles at a speed whichperiodically energizesthe heating element HE at the proper rate to keepit at the desired average temperature for which the control is set. Thelength of the cycles can be lengthened by raising the leaf spring 80 bymeans of the cam 66 controlled by the knob 14 as disclosed in Figure 8as it then takes greater warping force in the element 22 to separate itscontact 24 from the contact 26.

When the bimetal element 22 attains a predetermined temperature andconsequent relative deflection to a critical point, it begins tooscillate for control purposes at this point which corresponds to thecorrect blanket temperature as determined by the setting of the controlknob 14. Oscillation is produced because at a certain temperature thecontact 24 will disengage the contact 26 thus opening the circuit andpermitting the heater 32 to cool. The heat bridge element 33 and thebimetal element 22 likewise cool thus re-establishing the circuit byengagement of the contact 24 with the contact 26. The cycle thereuponrepeats the same as an electric buzzer or doorbell but the cycle is muchslower due to thermal lag between the heater 32 and the bimetal element22 because the heat must flow through the heat bridge element 33 beforereach ing the bimetal element.

In connection with a cycling switch of the character disclosed. it isdesirable that the cycle be automatically adjusted to follow room temerature conditions. This is accomplished by hav ing the contact 28mounted on the bimetal element 28 which tends to separate the contact 24from the contact 26 sooner at high room temperature than at low roomtemperature, as the tendency for the bimetal element 28 is to warpdownwardly upon ambient temperature rise. Such ambient tem erature risethus shortens the on cycles in relation to the off cycles of the heatingelement .T-TE' when room temperature rises and vice-versa. The bimetalelement 28 can be readily tailored to compensate for ambient temperatureor even over or under compensate for it if that is desirable. Ifreouired, the spring blade 8'! can also be made of bimetal for furthercompensation effect.

The heat brid e element 33 consists of a special mass of particulardimensions and particular thermal characteristics interposed between thebimetal element 22 and its heater 32. This mass of material need notnecessarily be of metal but preferably is metal for several reasons.Metal is easily fabricated in various desirable shapes of homogen usmasses and is economical to use. Metals are of various types and have awide ran e of thermal characteristics. They are also readily availableand different metals are comparatively easy to fabricate on the samedies to provide heat bridges having different heat flow characteristics.The heat flow characteristics of metal are relatively constant underwidely differing conditions which also make metal preferable. I havefound aluminum. brass and nickel-plated steel ouite suitable. By usingthe heat flow bridge element, the thermostat never reaches a state ofthermal stability and slow oscillation results as distinuished fromrapid oscillation in a buzzer or the like.

By slowly oscillating at the critical point, the bimetal 22 provides astable blanket temperature and of course the control point may be raisedor lowered as desired. The blanket and. the control unit are thus ineffect two sections of a parallel system with the control unit attaininga predetermined state of equilibrium at a comparatively high temperaturesuch as 195 degrees in the bimetal element 22 while the blanket attainsa state of equilibrium at a lower temperature, for instance degrees. Bythis method comparatively greater variations of bimetal temperature arepossible while having low blanket temperatures and a low range ofvariation of the blanket temperature.

The elements of the secondary control SC in Figure 6 do not enter intothe normal operation of the control unit disclosed but the unit SCoperates only in an emergency as when the heating element HE ispartially short-circuited or opencircuited. The operation of the unit SCis fully disclosed in my copending application, Serial No. 44,607, nowPatent No. d ed April 1952, and forms no part of the present inventionand accordingly its operation is omitted from the present specification.

Some changes may be made in the construction and arrangement of theparts of my temperature control unit without departing from the realspirit and purpose of my invention, and it is my intention to cover bymy claims any modified forms of structure or use of mechanicalequivalents which may be reasonably included within their scope.

I claim as my invention:

1. In a temperature control unit of the character disclosed, a cyclingtemperature responsive element, a room temperature responsive element,said elements being mounted in a housing responsive to room temperature,circuit control contacts carried by said elements for controlling acircuit to a heating element of an electrical appliance, a heater alsoin said circuit and arranged to heat said cycling temperature responsiveelement to cause the same to cycle, said heater heating said cyclingtemperature responsive element to a considerably higher temperature thanthe room temperature affecting said room temperature responsive element,an elongated heat bridge element having one end heated by said heaterand its other end connected with said temperature responsive element fordelaying the action of the cycling temperature responsive element inrelation to energization of said heater and de-energization thereofwherebv said cycling temperature responsive element cycles at asubstantially constant and relatively higher temperature than thetemperature of the appliance controlled by said temperature controlunit.

2. A temperature control unit comprising a temperature responsiveelement, circuit contacts controlled thereby, a heater in circuit withsaid contacts, said heater being provided to heat said temperatureresponsive element to cause the same to cycle, a heat bridge elementhaving said heater wound on one portion thereof and said temperatureresponsive element contacting another portion thereof spaced from saidfirst portion for delaying the action of the temperature responsiveelement in relation to energization and deenergization of said heaterand to cause the element to anticipate on and off cycles for the heatingelement of an appliance controlled by said control unit to keep it at asubstantially constant temperature relatively lower than the temperatureat which said temperature responsive element cycles, and a secondtemperature responsive element also controlling said contacts andresponsive to the ambient temperature of said unit for shortening the oncycles and lengthening the off cycles thereof in proportion to rise inroom temperature and vice-versa.

aeeaeee 3. Inatemperaturecontrol unit, a temperature cycling switchcomprising contacts for controlling the flower-current to aI-heatertype-electric appliance, a pair of thermally responsive elements foropening said contacts upon temperature rise, one of said contacts beingmagnetic and the other being of ferrous material to provide slight snapaction upon separation and engagement thereof, said contacts beingnormallylengaged at temperatures of the electric appliance lower thanthe desired temperature, .a heater in circuit with said contacts and invcircuit with the electric appliance, one of said thermally responsiveelements responding to the heat of said heater and being cycled therebyat a temperature substantially above .110 th room temperature and thetemperature at which the electric appliance cycles,

and the other of said thermally responsive elements being subject totemperature ambient to said unit for changing the proportions of the onand off cycles of said control unit depending on 5 room temperatureambient to said unit.

ALFRED J. HUCK.

References Cited in the file of this patent UNITED STATES PATENTS mNumber Name Date 1,980,756 Hoover Nov. 13, 1934 2,195,947 Uhlrig Apr..2, 1940 2,311,801 Ninans 'Feb. 23, 1943 1 2,354;9l8 Kearsley Aug. '1,1944 2,383,291 Cook l Aug. 21,1945 $518,941 Satc'hwell etal. l Aug. 15,1950

